RMVB has nothing to do with sprag/over running clutch failure except if the valve body doesn’t have low band apply. Really any valve body can have or not have low band apply. If you run a stock drum 727 you should have some style of containment regardless of any other part in the transmission. Low band apply make it a bit safer? Yes. I crushed a sprag in my 727 with low band apply. Due to the tire I run, I pedal the car a BUNCH in first gear. I believe the low band apply and to a lesser extent that the rollers were crushed and had locked the low reverse drum in place stopped it from going BOOM. It still cracked the case. Had to use long bolts in the tailshaft holes to push the low reverse drum out of the sprag! If it had shifted into sec……..ouch. No drum explosion, but it could have locked the tire or broken the low reverse drum free. I felt something in staging and while rolling into the burnout box and didn’t make the run.